The present invention relates generally to noise detection in sensed signals. Particularly, this invention relates to a system and method for digitally counting rejected noise signals provided by a motor drive or other sensor.
Motors operated in certain industrial settings are typically monitored for their in-line operational parameters so as to ensure their proper on-going operation, as well as for preempting motor malfunctions. Such in-line parameters may include motor speed, motor shaft angle, motor position and so forth. Detection of such parameters typically requires coupling sensors to the motor for detecting mechanical, thermal or electrical signals produced by or provided to the motor, from which various metrics are obtainable. Such metrics may provide indicators of certain operational states of the motor.
Electrical signals produced by motor-coupled sensors are typically susceptible to noise. Such noise may originate from the motor itself or from sources exterior to the motor, such as electrical wiring leading to or from the motor, wiring to and from the sensors to the motor, and wiring between the motor to motor monitoring units. Other ambient sources may include randomly produced electrical sources disposed in the vicinity of the motors and sensors. Current signal detection systems of motor motoring units are configured to detect signals, including noise related signals, such as by detecting whether time durations of pulses contained within the signal are longer than a certain threshold. Accordingly, pulses with time durations shorter than the threshold may be rejected by the detection system and, moreover, may not be registered, such that the number of pulses rejected by the detection system is not accounted for. In most instances, such pulses originate from noise which may go unregistered as motor performance is being monitored. By not counting the rejected noise signals, motor monitoring systems may be deprived of useful information obtainable from the rejected noise signals to the extent that uncertainties regarding maintenance of the motor and imminent malfunctions thereof may arise. Similarly, the nature and source of noise-causing disturbances are not appreciated, and in fact, are generally unknown due to the fact that noise itself is simply unappreciated.
There is a need in the art for improved techniques for monitoring noise in these and other systems. The technique is particularly needed in automation settings where noise can greatly affect the ability to monitor and control loads, and where some or most noise sources could be avoided if they were recognized and appreciated as such. Further, statistical analysis of rejected noise pulses is needed to provide a leading indicator of increasing noise levels, as well as a figure-of-merit to compare the noise levels from one system installation to another.